#include <bits/stdc++.h>
using namespace std;
double x01, y01, x02, y02, x03, y03;

int main() {
    cin >> x01 >> y01 >> x02 >> y02 >> x03 >> y03;
    double len1 = x01 - x02;
    double len2 = y01 - y02;
    double l1 = sqrt(len1 * len1 + len2 * len2);

    len1 = x01 - x03;
    len2 = y01 - y03;
    double l2 = sqrt(len1 * len1 + len2 * len2);

    len1 = x02 - x03;
    len2 = y02 - y03;
    double l3 = sqrt(len1 * len1 + len2 * len2);

    double p = (l1 + l2 + l3) / 2;

    double s = sqrt(p * (p - l1) * (p - l2) * (p - l3));

    cout << fixed << setprecision(2) << s;

    return 0;
}